Micro-machining system employing a two stage beam steering mechanism

ABSTRACT

A system for delivering energy to a substrate including a dynamically directable source of radiant energy providing a plurality of beams of radiation, each propagating in a dynamically selectable direction. Independently positionable beam steering elements in a plurality of beam steering elements are operative to receive the beams and direct them to selectable locations on the substrate.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 10/170,212 filed Jun. 13,2002, which claims benefit of Provisional Application No. 60/297,453filed Jun. 13, 2001; the above noted prior applications are all herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention generally relates to multiple laser beampositioning and energy deliver systems, and more particularly to lasermicro-machining systems employed to form holes in electrical circuitsubstrates.

BACKGROUND OF THE INVENTION

Various laser machining devices are used to micro-machine patterns insubstrates. Such systems typically are used in the manufacture ofelectrical circuit boards. Electrical circuit board manufacturecomprises depositing conductive elements, such as conductive lines andpads, on a non-conductive, typically dielectric, substrate. Several suchsubstrates are adhered together to form an electrical circuit board. Inorder to provide electrical interconnection between the various layersof an electrical circuit board, holes, called vias, are drilled throughselected substrate layers and plated with a conductor. Electricalcircuit boards typically include tens of thousands of vias, and as manyas several hundred thousand vias.

SUMMARY OF INVENTION

The present invention seeks to provide an improved laser micro-machiningapparatus, such apparatus being particularly useful to form vias inelectrical circuit boards.

The present invention still further seeks to provide an improved laserbeam positioning system operative to provide generally simultaneousindependent positioning of a plurality of laser beams.

The present invention still further seeks to provide lasermicro-machining apparatus employing a laser beam positioning systemoperative to provide simultaneous independent positioning of a pluralityof laser beams.

The present invention still further seeks to provide lasermicro-machining system operative to independently position a pluralityof pulsed laser beams, with a minimal loss in laser energy.

The present invention still further seeks to provide lasermicro-machining apparatus that efficiently utilizes laser energysupplied by a pulsed laser, such as a solid state Q-switched laser, togenerate vias in electrical circuit substrates.

The present invention still further seeks to provide lasermicro-machining apparatus that controls an energy property of a laserbeam by splitting an input laser beam into at least one output beamsthat are used to micro-machine a substrate. The at least one outputbeams may be a single beam or a plurality of beams.

The present invention still further seeks to provide a dynamic beamsplitter operative to split an input laser beam into a selectable numberof output sub-beams.

The present invention still further seeks to provide a dynamic beamsplitter operative to selectably split an input laser beam into aplurality of sub-beams having a generally uniform energy property.

The present invention still further seeks to provide a system forselectably deflecting a pulsed beam to a selectably positionable beamreflector pre-positioned in an orientation to suitable for deliveringenergy to a selectably location on a substrate. Deflection of the beammay be performed at a duty cycle which is at least as fast as a pulserepetition of the laser beam. Positioning of the reflector is performedat a duty cycle which is slower than the pulse repetition rate.

The present invention still further seeks to provide a dynamic beamsplitter operative to split an input laser beam into a plurality ofoutput laser beams, each of which is directed in a selectable direction.In accordance with an embodiment of the invention, each of the outputlaser beams is emitted from a different spatial section of the beamsplitter.

The present invention still further seeks to provide a laser beamdiverter operative to receive a plurality of laser beams generallypropagating in a common plane, and to divert each of the laser beams toa location in a two-dimensional array of locations outside the plane.

In accordance with a general aspect of an embodiment of the presentinvention, a laser beam positioning system, useful for example, tomicro-machine substrates, is operative to provide a plurality ofsub-beams which are dynamically deflected in a selectable direction.Each sub-beam is deflected so as to impinge on a deflector, located inan array of independently positionable deflector, whereat the sub-beamsare further deflected by the deflectors to impinge on a substrate at aselectable location. In accordance with an embodiment of the invention,the plurality of sub-beams is generated from a single input beam by adynamically controllable beam splitter.

In accordance with a general aspect of an embodiment of the invention, asystem for delivering energy to a substrate, includes a dynamicallydirectable source of radiant energy providing a plurality of beams ofradiation, propagating in a dynamically selectable direction.Independently positionable beam steering elements in a plurality of beamsteering elements are operative to receive the beams and direct them toselectable locations on the substrate.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a beam of radiation, a beamsplitter operative to split the beam into a plurality of sub-beams, eachsub-beam propagating in a selectable direction, and a plurality ofindependently positionable beam steering elements, some of which receivethe plurality of sub-beams and direct them to selectable locations onthe substrate.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a beam of radiation and adynamically configurable beam splitter disposed between the source ofradiant energy and the substrate.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a beam of radiation and anopto-electronic multiple beam generator disposed between the source ofradiant energy and the substrate. The multiple beam generator isoperative to generate at least two sub-beams from the beam and to selectan energy density characteristic of each sub-beam.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of pulsed radiant energy providing a pulsed beam ofradiation along an optical axis, the pulsed beam including multiplepulses separated by a temporal pulse separation, and a multiple beam,selectable and changeable angle output beam splitter disposed betweenthe source of radiant energy and the substrate. The selectable andchangeable angle output beam splitter is operative to output a pluralityof sub-beams at a selected angle relative to the optical axis. The angleis changeable in an amount of time that is less than the temporal pulseseparation.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of pulsed radiant energy providing a pulsed beam ofradiation, the pulsed beam including multiple pulses separated by atemporal pulse separation, a beam splitter disposed between the sourceof radiant energy and a substrate, the beam splitter being operative tooutput a plurality of sub-beams at selectable angles which arechangeable, and a plurality of selectable spatial orientationdeflectors. The deflectors are operative to change a spatial orientationin an amount of time that is greater than the temporal pulse separation.Some of the spatial orientation deflectors are arranged to receive thesub-beams and to direct the sub-beams to the substrate.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a beam of radiation, a beamsplitter operative to split the beam into a selectable number of outputbeams, the output beams having an energy property functionally relatedto the selectable number, a beam steering element receiving an outputbeam and directing the output beam to micro-machine a portion of asubstrate.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a plurality of beams ofradiation propagating in a plane and a plurality of deflectors receivingthe plurality of beams and deflecting at least some of the beams topredetermined locations outside the plane.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one source of radiant energy providing a beam of radiation, a beamsplitter operative to receive the beam and to output a plurality ofsub-beams propagating in a plane, and a plurality of deflectorsreceiving the plurality of sub-beams and deflecting at least some of theplurality of sub-beams to predetermined locations outside the plane.

In accordance with another general aspect of an embodiment of theinvention a method for delivering energy to a substrate comprisesdirecting a first plurality of beams of radiation onto a first pluralityof selectably positionable deflectors during a first time interval fordirecting the first plurality of beams onto a first plurality oflocations, during the first time interval, selectably positioning asecond plurality of selectably positionable deflectors, and during asecond time interval, directing the first plurality of beams ofradiation onto the second plurality of selectable positionabledeflectors for directing the first plurality of beams onto a secondplurality of locations.

In accordance with another general aspect of an embodiment of theinvention a system for delivering energy to a substrate comprises atleast one radiant beam source providing at least one beam of radiationand at least first and second deflectors disposed to receive the atleast one beam to deliver the beam to respective at least first andsecond at least partially overlapping locations on the substrate.

In accordance with another general aspect of an embodiment of theinvention a laser micro-machining apparatus includes at least oneradiant beam source providing a plurality of radiation beams, aplurality of independently positionable deflectors disposed between theat least one radiant beam source and a substrate to be micro-machined,the plurality of independently positionable deflectors being operativeto independently deliver the at least one radiation beam to selectablelocations on the substrate, and a focusing lens disposed between the atleast one radiant beam source and the substrate, the focusing lensreceiving the plurality of radiation beams and being operative tosimultaneously focus the beams onto the selectable locations on thesubstrate.

In accordance with another general aspect of an embodiment of theinvention an acousto-optical device includes an optical elementreceiving a beam of radiation along an optical axis, and a transducerassociated with the optical element, the transducer forming in theoptical element an acoustic wave simultaneously having differentacoustic frequencies, the optical element operative to output aplurality of sub-beams at different angles with respect to the opticalaxis.

In accordance with another general aspect of an embodiment of theinvention a method for micro-machining a substrate includes providing alaser beam to a beam splitter device, splitting the laser beam into afirst number of output beams and directing the first number of outputbeams to form at least one opening in a first layer of a multi-layeredsubstrate, and then splitting the laser beam into a second number ofoutput beams and directing ones of the second number of output beams toremove selected portions of a second layer of the multi-layeredsubstrate via the at least one opening.

Additional features and aspects of the invention include variouscombinations of one or more of the following:

The source of radiant energy comprises a pulsed source of radiant energyoutputting a plurality of beams each defined by pulses of radiantenergy.

The pulsed source of radiant energy comprises at least one Q-switchedlaser.

A dynamically directable source of radiant energy comprises a beamsplitter operative to receive a beam of radiant energy and splitting thebeam into a selectable number of sub-beams.

A dynamically directable source of radiant energy comprises a beamsplitter operative to receive a beam of radiant energy, to split thebeam into a plurality of sub-beams and to direct the sub-beams eachselectable directions.

The beam splitter comprises an acousto-optical deflector whose operationis governed by a control signal.

The beam splitter comprises an acousto-optical deflector having anacoustic wave generator controlled by a control signal, the acousticwave generator generating an acoustic wave which determines the numberof sub-beams output by the acousto-optical deflector.

The beam splitter comprises acousto-optical deflector having an acousticwave generator controlled by a control signal, the acoustic wavegenerator generating an acoustic wave which determines the selectabledirections of the sub-beams.

The acoustic wave in the acousto-optical deflector includes a pluralityof spatially distinct acoustic wave segments, each spatially distinctacoustic wave segment being defined by a portion of the control signalhaving a distinct frequency.

Each spatially distinct acoustic wave segment in the acoustic wavedetermines a corresponding spatially distinct direction of acorresponding sub-beam, which is a function of the frequency of theportion of the control signal corresponding to the acoustic wavesegment.

The number of spatially distinct acoustic wave segments determines thenumber of corresponding sub-beams.

The dynamically directable source of radiant energy comprises adynamically configurable beam splitter receiving a beam of radiantenergy and splitting the beam into a selectable number of sub-beams. Thedynamically configurable beam splitter is capable of changing at leastone of the number and direction of the sub-beams within areconfiguration time duration, and the pulses of radiant energy areseparated from each other in time by a time separation which is greaterthan the reconfiguration time duration.

The plurality of independently positionable beam steering elements iscapable of changing the direction of the sub-beams within a redirectiontime duration, and the pulses of radiant energy are separated from eachother in time by a time separation which is less than the redirectiontime duration.

Each of the beam steering elements includes a reflector mounted on atleast one selectably tilting actuator. The actuator comprises apiezoelectric device or a MEMs device.

The number of beam steering devices exceeds the number of sub-beamsincluded in the plurality of sub-beams. At least some of the pluralityof sub-beams are directed to at least some of the plurality of beamsteering devices while others of the plurality of the beam steeringdevices are being repositioned.

The selectable number of sub-beams all lie in a plane, a two dimensionalarray of beam steering elements lies outside the plane, and an array offixed deflectors optically interposed between the at least onedynamically directable source of radiant energy and the plurality ofindependently positionable beam steering elements is operative directthe beams lying in a plane to locations outside the plane.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1A is a simplified partially pictorial, partially block diagramillustration of a system and functionality for fabricating an electricalcircuit constructed and operative in accordance with a preferredembodiment of the present invention;

FIG. 1B is a timing graph of laser pulses output by a laser used in thesystem and functionality of FIG. 1;

FIG. 2 is a somewhat more detailed partially pictorial, partially blockdiagram illustration of part of an apparatus for micro-machiningelectrical substrates in the system and functionality of FIG. 1A;

FIG. 3 is a somewhat more detailed partially pictorial, partially blockdiagram illustration of an aspect of operation of part of the system andfunctionality of FIG. 2;

FIG. 4 is a flow diagram of a method for manufacturing electricalcircuits in accordance with an embodiment of the invention;

FIG. 5 is an illustration showing the result of varying the number andangle of laser beams produced by a dynamic beam splitter in the systemand functionality of FIGS. 1A and 2;

FIG. 6 is an illustration showing the result of varying the angle ofmultiple laser beams produced by a dynamic beam splitter in the systemand functionality of FIGS. 1A and 2;

FIG. 7 is an illustration showing the result of varying the angles ofmultiple at least partially superimposed laser beams produced by adynamic beam splitter produced by modulation control signals includingmultiple at least partially superimposed different frequency componentsin the system and functionality of FIGS. 1A and 2;

FIG. 8 is an illustration showing the result of varying the energydistribution among multiple laser beams produced by a dynamic beamsplitter in the system and functionality of FIGS. 1A and 2;

FIGS. 9A and 9B are illustrations showing the result of varying thenumber of uniform diameter laser beams produced by a dynamic beamsplitter in the system and functionality of FIGS. 1A and 2; and

FIGS. 10A and 10B are illustrations showing the result of varying thenumber of uniform diameter laser beams produced by a dynamic beamsplitter as shown in FIGS. 9A and 9B in accordance with a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1A, which is a simplified partiallypictorial, partially block diagram, illustration of a system andfunctionality for fabricating an electrical circuit, constructed andoperative in accordance with a preferred embodiment of the presentinvention, and to FIG. 1B which is a timing graph of laser pulses outputby a laser used in the system and functionality of FIG. 1A. The systemseen in FIG. 1A includes laser micro-machining apparatus 10, which alsoincludes the functionality of delivering energy to a substrate.

Apparatus 10 is particularly useful in the context of micro-machiningholes, such as vias 12, in printed circuit board substrates 14, duringthe fabrication of printed circuit boards. Apparatus 10 may also be usedin other suitable fabrication processes employing micro-machining,including without limitation, the selective annealing of amorphoussilicon in flat panel displays and the removal of solder masks onelectrical circuits. Accordingly, although the invention is described inthe context of micro-machining printed circuit boards, the scope of theinvention should not be limited solely to this application.

Printed circuit board substrates, such as a substrate 14, which aresuitable to be micro-machined using systems and methods describedhereinbelow, typically include dielectric substrates, for example epoxyglass, having one or more electrical circuit layers, each electricalcircuit layer having selectively formed thereon a conductor pattern 16.The substrates may be formed of a single layer or of a laminate formedof several substrate layers adhered together. Additionally, theoutermost layer of the substrate 14 may comprise the conductor pattern16 formed thereon, as seen in FIG. 1A. Alternatively, the outermostlayer of substrate 14 may comprise, for example, a metal foilsubstantially overlaying a continuous portion of the outer surface ofthe substrate 14, for example as shown by the region indicated byreference numeral 17.

In an embodiment of the invention, as seen in FIG. 1A, lasermicro-machining apparatus 10 includes a pulsed laser 20 outputting apulsed laser beam 22. Pulsed laser beam 22 is defined by a stream oflight pulses, schematically indicated by peaks 24 in laser pulse graph26 (FIG. 18). In accordance with an embodiment of the invention pulsedlaser 20 is a frequency tripled Q-switched YAG laser providing a pulseda UV laser beam 22 at a pulse repetition rate of between 10–50 KHz, andpreferably at about 10–20 KHz. Suitable Q-switched lasers are presentlyavailable, for example, from Spectra Physics, Lightwave Electronics andCoherent. Inc. all of California, U.S.A. Other commercially availablepulsed lasers, that suitably interact with typical materials employed tomanufacture printed circuit boards, may also be used.

Another laser suitable for use as pulsed laser 20, operative to output apulsed UV laser beam particularly suitable for micromachining substratescontaining glass, is described in the present Applicants' copending U.S.patent application Ser. No. 10/167,472, filed concurrently herewith andclaiming the benefit of U.S. provisional patent application 60/362,084,the disclosures of which are incorporated by reference in theirentirety.

In the embodiment seen in FIG. 1A, which is a highly simplifiedschematic representation of laser micro-machining apparatus 10, pulsedlaser beam 22 impinges on a first lens 28, which preferably is acylindrical lens operative to flatten beam 22 at an image plane (notseen) in a first variable deflector assembly, such as an acousto-opticaldeflector (AOD) 30. Preferably AOD 30 includes a transducer element 32and a translucent crystal member 34 formed of quartz or other suitablecrystalline material.

Transducer 32 receives a control signal 36 and generates an acousticwave 38 that propagates through crystal member 34 of AOD 30. Controlsignal 36 preferably is an RF signal provided by an RF modulator 40,preferably driven by a direct digital synthesizer (DDS) 42, or othersuitable signal generator, for example a voltage controlled oscillator(VCO). A system controller 44, in operative communication with DDS 42and a laser driver 47, is provided to coordinate between generation ofthe control signal 36 and laser pulses 24 defining pulsed laser beam 22so that portions of substrate 14 are removed, e.g. by ablation, inaccordance with a desired design pattern of an electrical circuit to bemanufactured. Such design pattern may be provided, for example, by a CAMdata file 46 or other suitable computer file representation of anelectrical circuit to be manufactured.

As known in the art, the presence of the acoustic wave 38 in crystalmember 34, when beam 22 impinges thereon causes beam 22 to be deflectedat an angle θ_(n) which is a function of the frequency f_(n) of wave 26according to the formula:

$\theta_{n} = \frac{\Delta\; f_{n} \times \lambda}{\upsilon_{s}}$Where:

-   -   Δf_(n)=f_(n)−f₀;    -   λ=wavelength of beam 22;    -   ν_(s)=speed of sound in the crystal 34 of AOD 30, and    -   n is an integer representing the index number of a laser        sub-beam, as described hereinbelow.

In accordance with an embodiment of the invention, AOD 30 is operativeto function as a dynamic beam splitter and which governs at least one ofa number segments into which beam 22 is split and its angle ofdeflection. Signal 36 may be selectably provided so as to cause acousticwave 38 to propagate at a uniform frequency through crystal member 34.Alternatively, signal 36 may be selectably provided so as to cause theacoustic wave 38 to propagate at different frequencies through thecrystal member 34.

Various aspects of the structure, function and operation of AOD 30 as adynamic beam splitter are described hereinbelow with reference to FIGS.5–7. The structure and operation of another type of AOD, configured andarranged to junction as a dynamic beam splitter and deflector isdescribed in the present Applicants' copending provisional patentapplication No. 60/387,911, filed concurrently herewith, entitled:“Dynamic Multi-Pass, Acousto-Optic Beam Splitter and Deflector”.

In accordance with an embodiment of the invention, signal 36 causes theacoustic wave 38 to be generated in AOD 30 with different frequenciessuch that at a moment in time the acoustic wave 38 interacts with thelaser pulse 24, the acoustic wave 38 comprises at least two differentfrequencies. By generating an acoustic wave 38 with more than onefrequency, beam 22 is split into more than one segment. Typically, thedifferent frequencies are spatially separated in AOD 30 at the time atwhich a laser pulse impinges thereon. Alternatively, the differentfrequencies are superimposed in a complex waveform.

Thus, when the acoustic wave 38 is propagated through crystal member 32in a non-uniform waveform and interacts with the laser beam 22, the beam22 is segmented into several beam segments 50, or sub-beams. Each of thesegments is deflected at an angle θ_(n) which is a function of anacoustic wave frequency, or frequencies, of the acoustic wave 38 incrystal member 34 at the time the laser beam 22, represented by peak 24(FIG. 1B), impinges thereon.

In accordance with an embodiment of the invention, AOD 30 operates at aduty cycle, which is less than the pulse repetition rate of laser beam22. In other words, the time required to reconfigure the acoustic wave38 in AOD 30 to comprise a different composition of frequencies whenimpinged upon by a laser pulse 24, so as to change at least one of thenumber of sub-beams 50 and the respective directions thereof at theoutput from AOD 30, is less than the time separation between sequentialpulses 24 in beam 22.

Each one of beam segments 50, whether a single segment provided e.g. bya uniform acoustic wave, or several segments as seen in FIG. 1, isdirected towards a second variable deflector assembly 52. The secondvariable deflector assembly 52 is formed of a plurality of independentlytiltable beam steering reflector elements 54.

In accordance with an embodiment of the invention, second variabledeflector assembly 52 comprises an optical MEMs device, or is formed asan array of mirrors tiltable by suitable piezo-electric motors, or isformed as an array of galvanometers, or comprises any other suitablearray of independently tiltable reflector devices. In the configurationof second variable deflector assembly 52 seen in FIG. 1A, a 6×6 array ofreflector elements 54 elements is provided. Any other suitable quantityof independently tiltable reflector elements 54 may be used.

A suitable optical MEMs device providing an array of independentlycontrollable digital light switches is employs technologies used in aDigital Micromirror Device (DMD™) available from Texas Instruments ofDallas, U.S.A. Alternatively, a suitable array of reflector elements 54may be constructed in accordance with fabrication principles of the DMD™described in detail in Mignardi et. al., The Digital MicromirrorDevice—a Micro-Optical Electromechanical Device for DisplayApplications, presented in MEMS and MOEMS Technology and Applications(Rai-Choudhury, editor), SPIE Press, 2000, the disclosures of which areincorporated herein by reference.

Each of the reflector elements 54 is operative to separately andindependently steer a beam segment 50 impinging thereon to impinge onthe substrate 14 at a selectable location in a target region 55 so as tomicro-machine, drill or otherwise remove a portion of substrate 14 atthe required location.

As seen in FIG. 1A, operation of reflector elements 54 may becontrolled, for example, by a servo controller 57 in operativecommunication with system controller 44 to ensure that reflectorelements 54 suitably direct beam segments 50 to impinge on substrate 14at a required location, in accordance with a desired design pattern ofan electrical circuit to be manufactured. Such design pattern may beprovided, for example, by the CAM data file 46 or other suitablecomputer file representation of an electrical circuit to bemanufactured.

Each of the reflector elements 54 is configured so that a beam impingingthereon may be steered to a selectable location in a correspondingregion of coverage. In accordance with an embodiment of the invention,the regions of coverage, corresponding to at least some of the reflectorelements 54, at least partially mutually overlap.

In accordance with an embodiment of the invention, the number ofreflector elements 54 in the second variable deflector assembly 52exceeds the maximum number of beam segments 50 output by AOD 30.Reflector elements 54 typically operate at a duty cycle which is slowerthan the pulse repetition rate of laser beam 22. In other words, thetime required to redirect a given reflector element 54 so that a beamsegment 50 impinging thereon may be redirected to a new location onsubstrate 14, is greater than the time separation between sequentialpulses 24 in beam 22.

Because of the redundancy in reflector elements 54, for any given pulse24 in beam 22, beam segments 50 are impinging on only some of thereflector elements 54., but not on others. Thus, reflector elements 54,which are not receiving a sub-beam 50, may be repositioned to a newspatial orientation, in preparation for receiving a sub-beam 50 from asubsequent laser pulse 24, while at generally the same time otherreflector elements 54 are directing beam segments 50 to impinge onsubstrate 14.

As seen in FIG. 1A, a folding mirror 62, a focusing lens 63 and atelecentric imaging lens 64 are interposed between second variabledeflector assembly 52 and substrate 14 to deliver beam segments 50 tothe surface of substrate 14. It is appreciated that the optical designof lenses 63 and 64 should accommodate beam segments 50 which propagatealong optical axes extending in mutually different directions.

It is further appreciated that as a function of system geometry andengineering design, a single folding mirror 62, no folding mirror ormultiple folding mirrors may be provided. Additionally focusing lens 63and telecentric lens 64 may be combined into a single optical element,or alternatively each of lenses 62 and 64 may comprise multiple lenselements. Moreover, system 10 may include a zoom lens (not shown)operative to govern a cross sectional dimension of one or more beamsegments 50, for example in order to form holes and vias on substrate 14having different diameters. Alternatively zoom optics may be employed toaccommodate and make uniform a diameter of beam-segments 50 which may beoutput by AOD with different diameters.

In accordance with an embodiment of the invention, the angles θ_(n) atwhich beam segments 50 are deflected by AOD 30 relative to the opticalaxis of the incoming beam 22 typically are very small, in the order of10⁻² radians. In order to provide for a more compact system, a beamangle expander, such as a telescoping optical element, schematicallyrepresented by lens 56, operative to increase the mutual angulardivergence of beam segments 50, preferably is provided downstream of AOD30.

AOD 30 generally is operative to deflect sub-beams 50 so that theoptical axes of beam segments 50 generally lie in a plane. As seen inFIG. 1A, second variable deflector assembly 52 comprises a twodimensional array that lies outside the plane of the optical axes ofbeam segments 50. As seen in FIG. 1A, a linear to 2-dimensional mappingassembly 58 is located between AOD 30 and the second variable deflectorassembly 52. Mapping assembly 58 receives beam segments 50, propagatingin the same plane, and redirects the beam segments 50 to a twodimensional array of locations outside the plane of the sub-beams 50.

In accordance with an embodiment of the invention, mapping assembly 58comprises a plurality of mapped sections 60 each of which are positionedin a suitable spatial orientation so that a beam segment 50 output byAOD 30 which impinges on a given mapped section 60 is directed to areflector element 54, to which it is mapped.

The following is a simplified general description of the operation andfunctionality of system 10: The acoustic wave is 38 is generated incrystal 34 in synchronization with the pulses 24 of beam 22 such that adesired acoustic wave structure is present in crystal member 34 at thetime a first laser beam pulse impinges thereupon. The acoustic wave 38may have a uniform frequency throughout crystal 34, which produces asingle beam segment 50. Alternatively, acoustic wave may have severaldifferent frequencies. Typically, the different frequencies may be, forexample, at various spatial segments along the length of acoustic wave38 to produce several somewhat spaced apart beam segments 50. Inaccordance with an embodiment of the invention, the duty cycle of AOD 30is sufficiently fast such that it can be dynamically reconfigured toselectably and differently split or deflect each pulse 24 in a beam 22.In a preferred embodiment of the invention, dynamic reconfiguration ofthe beam splitter is accomplished by forming acoustic waves havingmutually different structures in AOD 30 at the moment each pulse 24defining beam 22 impinges on AOD 30.

The different frequencies in acoustic wave 38 cause each beam segment 50to be deflected at a selectable angle θ_(n) to impinge on a selectedmapped section 60 of mapping assembly 58, preferably after passingthrough beam expander lens 56. Each beam segment 50 is directed by anappropriate mapped section 60 to a corresponding location on one ofreflector elements 54 at second variable deflector assembly 52. Thereflector element 54 is suitably tilted so that the beam segment 50 issubsequently further directed to a location on substrate 14 formicro-machining or drilling a required location of the substrate 14.

In accordance with an embodiment of the invention, although AOD 30operates at a duty cycle which generally is faster than the pulserepetition rate of laser beam 22, the deflection that it provides isrelatively limited in that it deflects beam segments 50 by relativelysmall angles of deflection. The beam segments 50 typically all lie inthe same plane.

Conversely, the time required to position individual reflector elements54 in second variable deflector assembly 52 typically is greater thanthe time separation between subsequent pulses defining laser beam 22.However, since each reflector element 54 may be tilted over a relativelylarge range of angles, preferable in at least 2-dimensions, a lasersub-beam 50 impinging on the reflector element 54 may be delivered tocover a relatively large spatial region.

In accordance with an embodiment of the invention, each of reflectorelements 54 is suitably tiltable so as that adjacent reflector elements54 are operable to deliver beam segments 50 to cover mutuallyoverlapping regions on the surface of substrate 14. Moreover, thereflector elements 54 in second variable deflector assembly 52 are ableto deliver beam segments 50 to substantially any location in the fieldof view 68 of the lenses 63 and 64.

After micromachining the desired portions 55 in the field of view 68,substrate 14 and apparatus 10 are mutually displaced relative to system10 so that the field of view 68 covers a different portion of thesubstrate 14.

In accordance with an embodiment of the invention, the number ofreflector elements 54 in assembly 52 typically exceeds the number ofbeam segments 50 into which laser beam 22 is split by AOD 30. During aninitial time interval, beam segments 50 impinge on a first plurality ofthe reflector elements 54, but not on other reflector elements 54. Theinitial time interval is used to reposition the other reflector elements54 which do not receive a beam segment 50, as described hereinbelow.

During a subsequent second time interval, beam segments 50 are deflectedby AOD 30 to impinge on at least some of the reflector elements 54 whichdid not receive beam segments 50 during the previous time interval. Thereflector elements 54 employed in the second time interval are nowsuitably repositioned to deflect the sub-beam 50 to the substrate 14.During the second time interval at least some of the reflector elementsthat are not impinged on by a beam segment 50, possibly includingreflector elements that were used in the first time interval, arerepositioned for use in a subsequent time interval. This process ofrepositioning reflector elements 54 that are not used during a giventime interval is repeated.

Stated generally, it may be said that concurrent to beam segments 50from a first laser pulse impinging on selected reflector elements 54,other reflectors are concurrently repositioned to receive beam segments50 from subsequent beam pulses.

Typically the time required to position a single reflector element 54 isin the order of between 1–10 milliseconds, corresponding to aboutbetween 20–200 pulses of a 20 KHz Q-switched laser. The length of time,which exceeds the duty cycle of the laser pulses 24, used to positionreflectors 54, ensures stabilized beam pointing accuracy. Additionally,the use of multiple reflectors 54 ensures a redundancy which minimizesthe loss of pulses while repositioning reflector 54 followingmicromachining of a location on substrate 14. It is appreciated that inorder to the increase the speed of the apparatus 10, and to provide acontrolled dosage of energy in each beam segment 50, it may be necessaryfor more than one beam segment 50 to simultaneously impinge on thesurface of substrate 14 at the same location. In such an arrangement,multiple beam segments 50 are each individually deflected to impinge onseparate reflectors 54, which are each oriented to direct the subbeams50 to impinge on substrate 14 at the same location.

Reference is now made to FIG. 2 which is a somewhat more detailedpartially pictorial, partially block diagram illustration of part of anapparatus 110 for micro-machining electrical circuits in the system andfunctionality of FIG. 1. In general, laser machining apparatus 110, maybe thought of as a system for delivering energy to a substrate.

In an embodiment of the invention, as seen in FIG. 1, lasermicromachining apparatus 110 includes a pulsed laser 120 outputting apulsed laser beam 122. Pulsed laser beam 122 is defined by a stream oflight pulses. In accordance with an embodiment of the invention pulsedlaser 20 is a frequency tripled Q-switched YAG laser providing a pulseda UV light beam 122 at a pulse repetition rate of between 10–50 KHz, andpreferably between about 10–20 KHz. Suitable Q-switched lasers arepresently available, for example, from Spectra Physics, LightwaveElectronics and Coherent, Inc. all of California, U.S.A. Othercommercially available pulsed lasers, that suitably interact withtypical materials employed to manufacture printed circuit boards, mayalso be used.

Another laser suitable for use as pulsed laser 120, operative to outputa pulsed UV laser beam particularly suitable for micromachiningsubstrates containing glass, is described in the present Applicants'copending U.S. patent application Ser. No. 10/167,472, filedconcurrently herewith and claiming the benefit of U.S. provisionalpatent application 60/362,084, the disclosures of which are incorporatedby reference in their entirety.

In the embodiment seen in FIG. 2, which is a highly simplified schematicrepresentation a preferred embodiment of laser micromachining apparatus110, a pulsed laser beam 122 impinges on a first lens 128, whichpreferably is a cylindrical lens operative to flatten beam 122 at animage plane (not seen) on a first variable deflector assembly, such asan acousto-optical deflector (AOD) 130. Preferably AOD 130 includes atransducer element 132 and a translucent crystal member 134 formed ofquartz or any other suitable crystalline material.

Transducer 132 is controlled by a control signal (not shown),corresponding to control signal 36 in FIG. 1A, and is operative togenerate acoustic waves 138 that propagate through crystal member 134 ofAOD 130, similarly as described with reference to FIG. 1A. The acousticwaves 138 are operative to interact with laser beam 122 in crystalmember 134 to dynamically and selectably split and deflect pulses inlaser beam 122, to output beam segments 150 or sub-beams 150.

AOD 130 is thus operative to function as a dynamic beam splitter whichcontrols, by forming a suitable acoustic wave 138 having a selectablewave configuration, at least one of a number segments 150 into whichbeam 122 is split and a direction at which the resulting beam segmentsare directed.

Various aspects of the structure, function and operation of AOD 130 as adynamic beam splitter are described hereinbelow with reference to FIGS.5–7. The structure and operation of another type of AOD configured andarrange to function as a dynamic beam splitter is described in thepresent Applicants' copending provisional patent application No.60/387,911, filed concurrently herewith, entitled; “Dynamic Multi-Pass,Acousto-Optic Beam Splitter and Deflector”.

In accordance with an embodiment of the invention, acoustic wave 138 maybe formed in AOD 30 with several different frequencies such that at amoment in time at which the acoustic wave 138 interacts with the laserbeam 122, the acoustic wave 138 comprises at least two differentfrequencies. By forming an acoustic wave 138 with more than onefrequency, beam 122 is split into more than one segments 150. Thedifferent frequencies may be spatially separated in AOD 130 at the timeat which a laser pulse impinges thereupon. Alternatively, the differentfrequencies may be superimposed in a complex waveform.

Thus when acoustic wave 138 is propagated through crystal member 132 ina non-uniform waveform, beam 122 may be segmented into several beamsegments 150, or sub-beams. Each of the beam segments 150 is deflectedat an angle θ_(n) which is a function of an acoustic wave frequency, orfrequencies, of acoustic wave 138 in crystal member 134 at the time alaser pulse in laser beam 122 impinges thereon.

In accordance with an embodiment of the invention, AOD 30 operates at aduty cycle which is shorter than the pulse repetition rate of laser beam122. Thus, the time required to reconfigure an acoustic wave 138 in AOD130 to comprise a different composition of frequencies when interactingwith a laser pulse in laser beam 122, so as to change at least one ofthe number and respective directions of sub-beams 150, is less than thetime separation between sequential pulses in laser beam 122.

Each one of beam segments 150, whether a single segment provided e.g. bya uniform acoustic wave, or several segments as seen in FIG. 2, isdirected to a first selectable target located at a second variabledeflector assembly 152. The second variable deflector assembly 152 isformed of a plurality of independently tiltable beam steering reflectorelements 154.

Each of the reflector elements 154 also operates to further separatelyand independently steer a beam segment 150, impinging thereon, toimpinge on substrate 14, as described with reference to FIG. 1A, andsubsequently to micro-machine, drill or otherwise remove a portion ofsubstrate 14 at such location.

In accordance with an embodiment of the invention, each reflectorelement 154 comprises a mirror 240, or another suitable reflectiveelement, mounted on a positioner assembly 242 comprising a base 244, amirror support 246, at least one selectable actuator 248, 3 actuatorsare shown assembled in a starlike arrangement, and a biasing spring (notshown). Each of the selectable actuators 248 is, for example, apiezoelectric actuator, such as a TORQUE-BLOCK™ actuator available fromMarco Systemanalyse und Entwicklung GmbH of Germany, independentlyproviding an up and down positioning as indicated by arrows 249 so as toselectively tilt mirror 240 into a desired spatial orientation forreceiving a beam segment 150 and subsequently to direct the beam segment150 to impinge on a desired location on the surface of substrate 14.

As appreciated from FIG. 2, considered along with FIG. 1A, each of theactuators 248 is operatively connected to a servo controller 57 which inturn is operatively connected to and controlled by system controller 44as described hereinabove with respect to FIG. 1A. Thus, it isappreciated that in correspondence to the a pattern design, for exampleof a pattern of vias in an printed circuit board, contained in CAM datafile 46, the relative spatial orientation, or tilt, of reflectorelements 154 is independently controlled in synchronization with thelaser pulses defining beam 122 and with the generation of control signalcontrolling the operation of AOD 130 to dynamically split and deflectlaser beam 122. A beam segment 150 is deflected to a desired reflectorelement 154, which in turn is suitably oriented so that the beam segment150 ultimately impinges on substrate 14 at a desired location.

In accordance with an embodiment of the invention, each of the reflectorelements 154 is configured so that a sub-beam 150 may be steered to aselectable location in a corresponding region of coverage on substrate14. The regions of coverage corresponding to at least some of thereflector elements 154 at least partially mutually overlap.

The number of reflector elements 154 in second variable deflectorassembly 152 typically exceeds the maximum number of beam segments 150output by AOD 130. Thus as seen in FIG. 2, second variable deflectorassembly includes 36 reflector elements, while 6 sub-beams 150 areoutput by AOD 130. Reflector elements 154 typically operate at a dutycycle which is less than the pulse repetition rate of laser beam 122.Thus, the time required to mechanically reposition a reflector element154, so that a beam segment 150 impinging thereupon may be redirected toa new location on substrate 14 is greater than the time separationbetween sequential pulses defining beam 122.

Because of the redundancy in reflector elements 154 over the respectiveof beam segments 150, for any given pulse in beam 122, beam segments 150are deflected to impinge on some reflector elements 154, but not onother reflective elements 154. Thus, some reflector elements 170 whichare not receiving a beam segment 150 may be repositioned to a newspatial orientation, in preparation for receiving a subsequent laserpulse 24, while at the same time other reflector elements 172, which arereceiving a beam segment 150, are directing the beam segments 150 toimpinge downstream, on substrate 14.

In accordance with an embodiment of the invention, the angles θ_(n) atwhich beam segments 150 are deflected by AOD 130 relative to the opticalaxis of the incoming beam 122 typically are very small, in the order of10⁻² radians. In order to provide for a more compact system, a beamangle expander, such as a telescoping optical element, schematicallyrepresented by lens 156, operates to increase the mutual angulardivergence of beam segments 150, preferably is provided downstream ofAOD 130.

AOD 130 generally is operative to deflect beams 50 so that the opticalaxes of beam segments 150 generally lie in the same plane, while secondvariable deflector assembly 152, comprising a two dimensional array thatlies outside the plane of the optical axes of beam segments 150.

A 2-dimensional mapping assembly 180 is interposed between AOD 130 andthe second variable deflector assembly 152. Mapping assembly 180receives beam segments 150, all generally propagating in a plane, andredirects the beam segments 150 to a two dimensional array of locationsoutside the plane of the sub-beams 150.

In accordance with an embodiment of the invention, mapping assembly 180comprises an array of support members 182 which comprise a plurality ofoptically transmissive portions 184, through which beam segments 150 canpass, and a plurality of reflective portions 186 operative to reflectbeam segments 150, which impinge thereupon.

As seen in FIG. 2, the reflective portions 186 generally are spacedapart on each support member 182, and the respective locations ofreflective portions 186 are preferably mutually laterally staggeredamong support members 182. Each reflective portion 186 is generallymapped to a corresponding reflector element 154. Consequently, each beamsegment 150 entering assembly 180 is received by the respectivereflective portion 186 on a first support member 187, or passes throughone or more support members until it is received by a reflective portion186 on one of the other support members 182.

Assembly 180 thus provides a means for redirecting beam segments 150,which propagate along optical axes lying in a plane of beam propagation,to impinge on a two dimensional array of locations lying outside theplane of propagation. AOD 130 selectively deflects a beam segment 150 toimpinge on one of the reflective portions 186 formed on one of thesupport members 182 in assembly 180. Because reflective portions 186intersect the plane of propagation at mutually staggered locations,along both an X axis and a Y axis in the plane of propagation, the angleat which a beam segment 150 is selectably deflected by AOD 130determines the reflective portion 186 on which it impinges. Thus, alocation in a two dimensional array of selectable locations, such as atsecond variable deflector assembly 152, lies outside the plane ofpropagation.

Reference is now made to FIG. 3 which is a somewhat more detailedpartially pictorial, partially block diagram illustration of an aspectof operation of part of the system and functionality of FIG. 2. Laserpulses 224 in a laser pulse timing graph 226 are designated 234, 236 and238 respectively. Laser 122 typically comprises laser pulses 224 whichare spaced time. Control signals 244, 246 and 248 are shown below laserpulses 234, 236 and 238 respectively. The control signals 244–248, forcontrolling the generation of the pulse 138 are shown being fed into atransducer 252 associated with an AOD 260. AOD 260 typically correspondsto AOD 130 in FIG. 2. Acoustic wave, corresponding to control signals264–268 are shown in AOD 260. Acoustic wave 264 corresponds to controlsignal 244, acoustic wave 266 corresponds to control signal 246 andacoustic wave 268 corresponds to control signal 244. For the purposes ofsimplicity of illustration, only a part of AOD 260 is shown for each oflaser pulses 224.

At a moment in time, corresponding to the emission of a laser pulse 224,an input laser beam 270 impinges on the AOD 260. The acoustic waves264–268 respectively cause laser beam 270 to be segmented into beamsegments, generally designated 250, each of which is deflected at anangle of deflection which is functionally related to correspondingfrequencies in acoustic waves 264–268.

First, second and third reflector elements, 280, 282 and 284respectively, corresponding to beam steering reflector elements 154 inFIG. 2, are shown below each of the AODs 260. At a time corresponding toeach laser pulse 224, a beam segment 250 is deflected to impinge on oneof the reflector elements 280, 282 and 284.

FIG. 3 also shows with particularity the timing relationship betweenlaser pulses 224, operation of AOD 260 as a dynamic beam deflectorhaving a duty cycle which is faster than the pulse repetition raterepresented by pulses 224, and operation of reflector elements 280, 282and 284., having a duty cycle which is slower than the pulse repetitionrate

As previously noted, the reconfiguration time required to introduce adifferent acoustic wave into AOD 260 is less than the time separationbetween pulses 234. Thus, the respective waveforms of control signals244–248, and the respective waveforms of acoustic waves 264–268 are eachdifferent thereby resulting in the selectable deflection of beamsegments 250 for each of pulses 224. It is noted however, that in thesequentially provided control signals 244 and 246, and correspondingsequentially provided acoustic waves 264 and 266, the frequency in afirst spatial wave segment 290 changes, while the frequency in a secondspatial wave segment 292 remains unchanged.

For both pulses 234 and 236, a first beam segment 294, corresponding tothe second spatial wave segment 292, impinges on third reflector element284. Reflector element 284 is held stationary to receive the first beamsegment 294 for each of pulses 234 and 236 respectively.

A second beam segment 296 is deflected in a first direction by firstspatial segment 290 of acoustic wave 264, while a third beam segment 298is deflected in a different direction by first spatial segment 290 inacoustic wave 266.

Moreover, for pulses 234 and 236, neither of the beam segments 250impinge on first and second deflector elements 280 and 282 respectively,but rather are directed to other deflector elements which are not shown.The time interval between pulses 234 and 236 is utilized to spatiallyreposition the first and second reflector elements 280 and 282.

A new wave form of acoustic wave 268 is formed in AOD 260 to selectablysplit and deflect beam 270 at pulse 238. As seen below pulse 238, noneof the beam segments 250 impinge on first reflector element 280 or thirdreflector element 284.

A fourth beam segment 300 impinges on deflector element 282. Beamsegment 300 is deflected in a direction that is functionally related tothe frequency of acoustic wave 268 in second spatial segment 292. It isnoted that the frequency in the second spatial segment 292 of acousticwave 268 has been changed relative to the acoustic waves 264 and 266. Afifth beam segment 302 is deflected in a direction that is functionallyrelated to the frequency of acoustic wave 268 in first spatial segment290.

It is thus noted from the foregoing that the repositioning time ofreflector elements 280–284, such as beam steering reflector elements154, is slower than a time separation between pulses 224. Nevertheless,because the reconfiguration time of dynamic beam splitter is less thanthe time separation between pulses, any redundant reflector elements canbe repositioned over a time interval greater than the separation betweenpulses. A reflector element that is in a suitable position can then beselected in a time interval that is less than the time separationbetween pulses.

Reference is now made to FIG. 4 which is a flow diagram 320 of amethodology for manufacturing electrical circuits in accordance with anembodiment of the invention. The methodology is described in the contextof a process for forming micro vias in a multi layered printed circuitboard substrate having a metal foil layer overlaying a dielectricsubstrate.

The presently described methodology for manufacturing electricalcircuits employs at least one dynamically directable source of radiantenergy providing a plurality of beams of radiation, each beampropagating in a dynamically selectable direction. The beams areselectably directed to a plurality of independently positionable beamsteering elements. Some of the beam steering elements receive the beamsand direct them to selectable locations on a printed circuit boardsubstrate to be micro-machined.

Suitable apparatus for generating a plurality of beams propagating indynamically selectable directions is the laser micro-machining apparatus10 is described with reference to FIG. 1A, and laser micro-machiningapparatus 110 described with reference to FIG. 2. Thus beams propagatingin dynamically selectable directions may be produced, for example, bypassing one or more beams output by at least one Q-switched laserthrough at least one dynamic beam splitting and deflecting device.Optionally, several separately generated beams may be treated separatelyor in combination.

In accordance with an embodiment of the invention, the dynamic deflectordevice is operable to selectably provide at least one metal machiningbeam-segment. In an embodiment of the invention, a beam splittingfunctionality is provided by the dynamic deflector, although a separatebeam splitting device providing a selectable beam splitting function maybe provided. The metal-machining beam-segment has an energy density thatis suitable to remove a portion of the metal foil layer, for example byburning or by ablation.

Each metal machining beam segment is dynamically deflected to impinge ona beam steering device, such as a tiltable reflector element 154 in FIG.2. The beam steering device is suitably positioned so that the metalmachining beam segment is steered to a selectable location on a PCBsubstrate whereat a portion of the metal foil is removed to expose theunderlying dielectric substrate.

While a metal machining beam is removing a portion of the metal foil ata first location, beam steering devices which are not being presentlyused may be suitably repositioned for removal of metal foil at otherselectable locations. Thus, each subsequent pulse may be deflected bythe dynamic beam deflector to impinge on an already positioned beamsteering device.

Removal of portions of the metal foil continues at selectable locationsuntil metal foil is removed for a desired plurality of locations.

In a subsequent operation, the dynamic deflector device is provide atleast one dielectric machining beam-segment having an energy propertythat is different from the metal machining beam-segment. A beamsplitting functionality may be provided, for example by the dynamicdeflector or by a suitable beam splitter device. For example, dielectricmachining beam segment has a lower energy density than a metal machiningbeam-segment. The energy property of the dielectric machining beamsegment is suitable to remove a portion of the dielectric layer, forexample by burning or by ablation, but is not suitable to remove aportion of the metal foil.

In accordance with an embodiment of the invention, the respective energydensities of beam segments 50 and 150 are controlled by splitting laserbeam 22 and 122 into a selectable number of beam segments 50 and 150,and by maintaining the diameter of the resulting beam segment 150irrespective of the number of beam segments.

Each dielectric machining beam segment is dynamically deflected toimpinge on a beam steering device, such as a tiltable reflector element154 in FIG. 2. The beam steering device is suitably positioned so thateach dielectric machining beam segment is steered to a selectablelocation whereat a portion of the metal foil has already been removed,to expose of the dielectric layer, and a desired portion of thedielectric is removed.

While a dielectric machining beam is removing a portion of thedielectric at a first set of locations, beam steering devices which arenot being presently used may be suitably repositioned for removal ofdielectric at other selectable locations. Thus, each subsequent pulsemay be deflected by the dynamic beam deflector to impinge on an alreadypositioned beam steering device. It is appreciated that because areduced energy density is required to remove dielectric, beam 122 may bedivided into a greater number of dielectric machining beam segments,resulting in a greater system throughput for removing dielectric ascompared to removing metal foil.

Removal of dielectric continues at selectable locations until thedielectric is removed for substantially all of the locations at whichmetal foil was previously removed. Once this operation is completed, asubstrate can be repositioned for micro-machining of a subsequentportion thereof.

As noted above, in accordance with an embodiment of the presentinvention, an AOD is configured and operative to dynamically andselectably split an incoming beam of radiation into a selectable numberof beam segments, each of which is dynamically directed in a selectabledirection.

Reference is now made to FIG. 5, which is an illustration of varying thenumber and angle of laser beams produced by a dynamic beam splitter inthe system and functionality of FIGS. 1 and 2. Laser pulses 424 in alaser pulse timing graph 426 are designated 434, 436 and 438respectively. Laser pulses 424 define, for example, beam 122 in FIG. 2and are mutually separated in time.

Control signals 444, 446 and 448 are shown above laser pulse timinggraph 426, corresponding to pulses 434, 436 and 438 respectively. Thecontrol signals 444–448 are shown being fed into a transducer 452associated with an AOD 460, corresponding to AOD 130 in FIG. 2. Acousticwaves, 464, 466 and 468, corresponding to control signals 444–448 areshown in AOD 460. Acoustic wave 464 corresponds to control signal 444,acoustic wave 466 corresponds to control signal 446 and acoustic wave468 corresponds to control signal 448.

At a moment in time corresponding to the emission of a laser pulse 424,an input laser beam 470 impinges on the on AOD 460. The acoustic waves464–468 respectively cause laser beam 470 to be segmented into aselectable number of beam segments, generally designated 450. Each ofthe beam segments 450 is deflected at an angle of deflection which isfunctionally related to a corresponding frequency in a portion ofacoustic waves 464–468.

FIG. 5 shows with particularity the timing relationship between laserpulses 424 and operation of AOD 460 as a dynamic beam splitter which isoperative to split an input beam 470 into a selectable number of beamsegments 450 at a duty cycle which is less than the pulse repetitionrate represented by pulses 424.

A control signal 444 having a generally uniform frequency generates anacoustic wave 464 in AOD 460 also having a generally uniform frequency.When the beam 470 associated with pulse 434 impinges on AOD 460, asingle beam-segment 480 is output. It is noted that a part of beam 470may not be deflected. This is ignored for the purposes of simplicity ofillustration.

A control signal 446 having a six spatially distinct segments 482–492,each segment having a generally uniform frequency and a frequency whichis different from a neighboring segment, generates an acoustic wave 466in AOD 460 also having six spatially distinct segments 502, 504, 506,508, 510 and 512. Each of the spatially distinct segments 502–512respectively has a generally uniform acoustic frequency and an acousticfrequency which is different from a neighboring segment. When the beam470 associated with pulse 436 impinges on AOD 460, six distinctbeam-segments 522–532 are output. It is noted that a part of beam 470may not be deflected. This is ignored for the purposes of simplicity ofillustration.

A control signal 448 having a two spatially distinct segments 542 and544, each segment having a generally uniform frequency and a frequencywhich is different from its neighboring segment, generates an acousticwave 468 in AOD 460 also having two spatially distinct segments 562 and564. Each of the spatially distinct segments 562 and 564 respectivelyhas a generally uniform acoustic frequency and an acoustic frequencywhich is different from its neighboring segment. When the beam 470associated with pulse 438 impinges on AOD 460, two distinctbeam-segments 572 and 574 are output. It is noted that a part of beam470 may not be deflected. This is ignored for the purposes of simplicityof illustration.

In the embodiment seen in FIG. 5, the division of a beam 470 intodifferent numbers of beam-segments 450 results in beam segments 450 eachhaving different a different width. In such embodiment it may bedesirable to provide suitable optics downstream of AOD 460 in order tocontrol the size of a spot impinging on a substrate 14, resulting fromeach different number of beam-segments 450, for example to ensure auniform diameter.

Reference is now made to FIG. 6, which is an illustration of varying theangle of multiple laser beams produced by a dynamic beam deflector inthe system and functionality of FIGS. 1A and 2. Laser pulses 624 in alaser pulse timing graph 626 are designated 634 and 636 respectively.Laser pulses 624 define, for example, beam 22 in FIG. 1 and beam 122 inFIG. 2, and are mutually separated in time.

Control signals 644 and 646 are shown above laser pulse timing graph626, corresponding to pulses 634 and 636 respectively. The controlsignals 644 and 646 are shown being fed into a transducer 652 associatedwith an AOD 660, corresponding to AOD 30 in FIG. 1 and AOD 130 in FIG.2. Acoustic waves, corresponding to control signals 644 and 646 areshown in AOD 660. Acoustic wave 664 corresponds to control signal 644,and acoustic wave 666 corresponds to control signal 646.

At a moment in time corresponding to the emission of a laser pulse 624,an input laser beam 670 impinges on the on AOD 660. The acoustic waves664 and 666 respectively cause laser beam 670 to be segmented into aselectable number of beam segments, generally designated 650, asdescribed with reference to FIG. 5. Each of the beam segments 650 isdeflected at an angle of deflection which is functionally related to acorresponding frequency in a portion of acoustic waves 664–666.

FIG. 6 shows with particularity the timing relationship between laserpulses 634 and operation of AOD 660 as a dynamic beam splitter which isoperative to split the input beam 670 into a selectable number of beamsegments 650, and to separately deflect the beam segments 650 atdistinct angles of deflection, all at a duty cycle which is less thanthe pulse repetition rate represented by pulses 624.

A control signal 644 having a six spatially distinct segments 682–692,each segment having a generally uniform frequency and a frequency whichis different from a neighboring segment, generates an acoustic wave 664in AOD 660 also having six spatially distinct segments 702, 704, 706,708, 710 and 712. Each of the spatially distinct segments 702–712respectively has a generally uniform acoustic frequency and an acousticfrequency which is different from a neighboring segment. When the beam670 associated with pulse 634 impinges on AOD 660, six distinctbeam-segments 722–732 are output. It is noted that the respectivefrequencies in each of segments 702–712 progressively increases,relative to the previous segment, and as a result the angle at whichbeams 722–732 are deflected increases in a corresponding manner.

A control signal 646 having a six spatially distinct segments 742–752,each segment having a generally uniform frequency and a frequency whichis different from a neighboring segment, generates an acoustic wave 666in AOD 660 also having six spatially distinct segments 762, 764, 766,768, 770, and 772 respectively. Each of the spatially distinct segments762–772 respectively has a generally uniform acoustic frequency and anacoustic frequency which is different from a neighboring segment. Whenthe beam 670 associated with pulse 636 impinges on AOD 660, six distinctbeam-segments 782–790 are output, in which beam-segment 782 correspondsto acoustic wave segment 762, beam-segment 784 corresponds to acousticwave segment 764, beam-segment 786 corresponds to acoustic wave segment766, beam-segment 788 corresponds to acoustic wave segment 768,beam-segment 790 corresponds to acoustic wave segment 770, andbeam-segment 792 corresponds to acoustic wave segment 792.

It is seen that the arrangement of respective frequencies in each ofacoustic wave segments 762–772 does not change in an orderly manner. Asa result some of beams 782–790 overlap. This enables beams 782–790 to beselectably deflected to impinge, for example on a mapping element 60(FIG. 1). It is further noted that the change in angles occurring inbeams 782–792, relative to beams 722–732 results from thereconfiguration of the acoustic wave in AOD 660. Accordingly, the changein configuration of the acoustic wave, from acoustic wave 664 toacoustic wave 666, is carried out in a period of time that is less thanthe time separation between pulses 634 and 636.

Reference is now made to FIG. 7 which is an illustration of varying theangles of multiple at least partially superimposed laser beams producedby a dynamic beam splitter, by modulating, for example control signals36, including multiple at least partially superimposed differentfrequency components, in the system and functionality of FIGS. 1A and 2.A control signal 844 is shown being fed into a transducer 852 associatedwith an AOD 860, corresponding to AOD 30 in FIG. 1 and AOD 130 in FIG.2. An acoustic wave 864, corresponding to control signal 844 is shown inAOD 860.

Control signal 844 corresponds to a mutual superimposition of threecontrol signals (not shown) each having a different frequency. It isnoted that a greater or lesser number of control signals may besuperimposed, and that superimposition of three control signals ischosen merely for the purposes of simplicity of illustration.

At a moment in time corresponding to the emission of a laser pulse in apulsed laser beam 22 or 122, an input laser beam 870 impinges on the onAOD 860 and is split into three beam segments 880, 882 and 884. Each ofthe beam segments 880–884 has a generally uniform width generallyrelated to the width of acoustic wave 864 in AOD 860. Each of the beamsegments 880, 882 and 884 is deflected at an angle functionally relatedto one of the frequency components is acoustic wave 864, and at leastpartially mutually overlap.

Reference is now made to FIG. 8 which is an illustration of varying theenergy distribution among multiple laser beam segments produced by adynamic beam splitter in the system and functionality of FIGS. 1A and 2.Typically, due to the Gaussian energy profile of typical laser beams, auniform spatial splitting of the beam results in beam segments, such asbeam segments 150 in FIG. 2, which do not have a uniform energyproperty. It is appreciated, that a beam shaping element, locatedupstream of the dynamic beam splitter, may be provided to form a beam,such as beam 22 or 122, which has a non-Gaussian, preferably top-hatshaped energy profile. In accordance with an embodiment of theinvention, presently described, sub-beams having a generally uniformenergy characteristic that is formed without using an external beamshaping element. Additionally, an energy characteristic of the sub beamsmay be changed in a time which is less than a separation time betweenpulses in a pulsed laser.

In FIG. 8, laser pulses 924 in a laser pulse timing graph 926 aredesignated 934 and 936 respectively. Laser pulses 924 define, forexample, beam 122 in FIG. 2 and are mutually separated in time. An inputenergy graph 940 indicates a typical Gaussian energy characteristic, inone dimension, of a laser beam such as beam 122.

Control signals 944 and 946 are shown above laser pulse timing graph926, and correspond to pulses 934 and 936 respectively. The controlsignals 944 and 946 are shown being fed into a transducer 952 associatedwith an AOD 960, corresponding to AOD 30 in FIG. 1 and AOD 130 in FIG.2. Acoustic waves, corresponding to control signals 944 and 946 areshown in AOD 960. Acoustic wave 964 corresponds to control signal 944and acoustic wave 966 corresponds to control signal 946.

At a moment in time corresponding to the emission of a laser pulse 924,an input laser beam 970 impinges on the AOD 960. The acoustic waves 964and 966 respectively cause laser beam 970 to be segmented into aselectable number of beam segments, generally designated 950. Each ofthe beam segments 950 is deflected at an angle of deflection which isfunctionally related to a corresponding distinct frequency in a portionof acoustic waves 964 and 966, and the width of beam segments is relatedto the width of a portion of acoustic waves 964 and 966 which has adistinct frequency.

It is seen in FIG. 8 that signal 944 is divided into six segments 945which are not of equal width. The resulting acoustic wave 964 thus islikewise formed of six segments which are not of equal width. Moreover,the respective widths of the resulting beam segments 972–982 are alsonot equal.

It is appreciated that the respective widths of segments 945, can bedynamically arranged and modified to produce beam segments, which,although having different spatial widths, have a generally uniformenergy characteristic. Thus the selectable division of acoustic wave 964into non-uniform segments 945 produces a selectable energycharacteristic of each beam 972–982, indicated by the area under outputenergy graph 984. For example, the dynamic splitting of beam 970 can besuch that a relatively small spatial section of a high energy portion ofbeam 970 is used to produce beam segments 976 and 978, a relativelylarge spatial section of a low energy portion of beam 970 is used toproduce beam segments 972 and 982, and an intermediate size spatialportion of beam 970 is used to produce beam segments 974 and 980. Energyuniformity is seen in histogram 990.

Thus, energy uniformity of output beam segments may be controlled andmade generally uniform by distributing energy among beam segments972–982, generally without attenuating the energy of input beam 970.Moreover, energy uniformity may be controlled independently of thenumber of beam segments 984 into which beam 970 is split, or thedirection of deflection of respective beam segments. In accordance withan embodiment of the invention, suitable optics (not shown) are provideddownstream of AOD 960 in order to accommodate and control the respectivediameters of beam-segments 972–982, each of which have a differentwidth, but generally uniform energy distribution.

In FIG. 8 it is also seen that the energy distribution among beamsegments 972–982 may be varied between pulses 924. Thus in the graphsassociated with pulse 936, segments 1005 of control signal 946 have beenmade generally uniform. As a result, the spatial width of each of thebeam segments 950 resulting from acoustic wave 966 is generally uniform,however the energy distribution among the beam segments resulting frominteraction of acoustic wave 966 and beam 970 is not uniform, as shownby histogram 1010.

Uniformity of an energy characteristic among beam segments formed by anacoustic wave 966 may be improved, for example by providing a beamshaping element (not shown) external to AOD 960 and operative to shapethe energy profile of input beam 970. Alternatively, the power ofacoustic wave 966 at various segments 1015, represented by convention asan amplitude, may be varied. In generally an increase power of acousticwave 966 results in a higher transmissivity through an AOD, namely arelatively greater portion of energy passes through AOD 960. Thus inorder to provide sub-beams 950, and 972–982 having a generally uniformenergy characteristic, an energy characteristic of beam segments whichare formed from a spatial portion of 970 having a relatively high energylevel may be attenuated by reducing thereat the power of acoustic wave966.

FIGS. 9A and 9B are illustrations of varying the number of uniformdiameter laser beams produced by a dynamic beam splitter in the systemand functionality of FIGS. 1 and 2. As seen in FIGS. 9A and 9B a beamsize modifier 1120 is provided to selectably change the size of an inputbeam 1170 impinging on an AOD 1130. The beam size modifier may be, forexample, a beam expander, zoom lens or cylindrical telescope.

As seen in FIG. 9A, a modified size beam 1172 is output from beam sizemodifier 1120. In the example seen in FIG. 9A, the modified size beam1172 impinges on only a portion of AOD 1130, thereby reducing anoperative portion of AOD 1130. A control signal 1136 is provided to forman acoustic wave 1138 in AOD 1130, which in turn is operative toselectably split modified size beam 1172 into two beam segments 1150each having, for example, a standardized modular size.

As seen in FIG. 9B, a modified size beam 1182 is output from beam sizemodifier 1120. In the example seen in FIG. 9B, the size of beam 1182 isdifferent from beam 1172, is substantially not modified respective ofbeam 1170 and impinges on substantially and entire operative portion ofAOD 1130. A control signal 1146 is provided to form an acoustic wave1148 in AOD 1130, which in turn is operative to selectably split beam1182 into six beam segments 1190. Each of beam segments have, forexample, a standardized modular size corresponding to the size of beamsegments 1150.

FIGS. 10A and 10B are an illustration of varying the number of uniformdiameter laser beams produced by a dynamic beam splitter as shown inFIG. 9 in accordance with a preferred embodiment of the presentinvention. An array 1200 of partially transmissive beam splitterelements 1202–1212 is provided in cascade to produce a plurality ofseparated beam segments, which are provided to a dynamic beam deflector1230.

The transmissivity of each beam splitter element is determined as afunction of its location relative to a last beam splitter element in thearray. Thus, as seen in FIGS. 10A and 10B, a first beam splitter element1202 deflects 16.7% of the input beam , a second beam splitter element1204 deflects 20% of the input beam reaching it, a third beam splitterelement 1206 deflects 25% of the input beam reaching it, a fourth beamsplitter element 1208 deflects 33.3% of the input beam reaching it, afifth beam splitter element 1210 deflects 50% of the input beam reachingit, and a sixth and last beam splitter element 1212 deflects 100% of theinput beam reaching it.

As seen in FIG. 10A, all of the beam splitter elements 1202–1212 arepositioned in line to receive a laser input beam 1222, and a pluralityof six distinct beam segments 1224, each having about 16.7% of the totalenergy in input beam 1222, are output to impinge on a dynamic beamdeflector 1230. A spatially sectioned acoustic wave 1238 is formed inAOD 1230 and is operative to dynamically deflect each of beam segments1222, generally as described hereinabove.

As seen in FIG. 10B, beam splitter elements 1202–1208 are out of theoptical path of laser input beam 1222, such that beam 1222 firstimpinges on beam splitter element 1210. Only two distinct beam segments1226, each having about 50% of the total energy in input beam 1222, areoutput to impinge on a dynamic beam deflector 1230. A spatiallysectioned acoustic wave 1238 is formed in AOD 1230 and is operative todynamically deflect each of beam segments 1222, generally as describedhereinabove.

It is noted, from the foregoing description with respect to FIGS. 5–10B,that an a dynamic deflector comprises an AOD and is operative to performat least on of the following functionalities: selectably split an inputbeam into a selectable number of output beams, to select an energycharacteristic of the output beams, and to direct the output beams eachat a selectable angle.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the present invention includesmodifications and variations thereof which would occur to a person ofskill in the art upon reading the foregoing description and which arenot in the prior art.

1. A method for micromachining a substrate, comprising: providing apulsed beam of radiation, said pulsed beam including multiple pulsesseparated by a temporal pulse separation; at a first element, comprisinga changeable output beamsplitter, splitting said pulsed beam into aplurality of sub-beams and outputting said plurality of sub-beams atselectable angles, wherein a number of said plurality of sub-beams andthe selectable angle of each of said sub-beams are changeable in anamount of time that is less than said temporal pulse separation; and ata second element, comprising a plurality of deflectors, deflecting eachof the plurality of sub-beams from one of said plurality of deflectorsin a selectable direction based on orientations of said plurality ofdeflectors, wherein an orientation of each of said plurality ofdeflectors is changeable in a redirection time period which is greaterthan said temporal pulse separation.
 2. The method claimed in claim 1and wherein said providing comprises generating said pulsed beam ofradiation, said pulsed beam including a pulsed laser beam, using atleast one pulsed laser.
 3. The method claimed in claim 2 and whereinsaid at least one pulsed laser is a Q-switched laser.
 4. The methodclaimed in claim 1 and wherein said providing comprises generating saidpulsed beam using a Q-switched laser.
 5. The method claimed in claim 1and wherein said splitting also comprises: providing an acousto-opticaldeflector as said first element; and controlling said acousto-opticaldeflector.
 6. The method claimed in claim 5 and wherein said controllingcomprises: generating an acoustic wave; and determining said selectablenumber of sub-beams.
 7. The method claimed in claim 5 and wherein saidcontrolling comprises: generating an acoustic wave; and determining saidselectable angles of said sub-beams.
 8. The method claimed in claim 6and wherein said controlling also comprises: determining said selectableangles of said sub-beams.
 9. The method claimed in claim 8 and whereingenerating said acoustic wave comprises: generating a plurality ofspatially distinct acoustic wave segments; and defining each spatiallydistinct acoustic wave segment by a portion of a control signal having adistinct frequency.
 10. The method claimed in claim 9 and alsocomprising: determining a corresponding spatially distinct angle of acorresponding sub-beam from said each spatially distinct acoustic wavesegment, said distinct angle being a function of the frequency of theportion of the control signal corresponding to said acoustic wavesegment.
 11. The method claimed in claim 9 and also comprising:determining the number of corresponding sub-beams from the number ofsaid spatially distinct acoustic wave segments.
 12. The method claimedin claim 2 and also comprising: providing said plurality of deflectors,each mounted on at least one selectably tilting actuator.
 13. The methodclaimed in claim 12 and wherein said at least one actuator comprises apiezoelectric device.
 14. The method claimed in claim 12 and whereinsaid at least one actuator comprises a MEMs device.
 15. The methodclaimed in claim 1 and also comprising: providing said plurality ofdeflectors, wherein a number of said plurality of deflectors exceeds amaximum number of said plurality of sub-beams; and while said pluralityof sub-beams is directed to a first collection of said plurality ofdeflectors, simultaneously changing orientations of a second collectionof said plurality of deflectors.
 16. The method claimed in claim 1 andwherein said plurality of sub-beams all lie in a single plane.
 17. Themethod claimed in claim 15 and wherein said plurality of deflectorscomprises a two dimensional array of deflectors.
 18. The method claimedin claim 17 and also comprising: at a third element comprising an arrayof fixed deflectors, deflecting said plurality of sub-beams.
 19. Themethod claimed in claim 1 and also comprising: using said plurality ofsub-beams to remove portions of said substrate at specific locations.20. The method claimed in claim 1 and wherein said plurality ofsub-beams comprises at least two sub-beams directed at differentselected angles.
 21. A method for micromachining a substrate,comprising: providing a pulsed beam of radiation, said pulsed beamincluding multiple pulses separated by a temporal pulse separation; at afirst element, splitting said pulsed beam into a plurality of sub-beamsand outputting said plurality of sub-beams at selectable angles, whereina selectable number of said plurality of sub-beams and said selectableangles are changeable in a redirection time period time that is lessthan said temporal pulse separation; receiving said plurality ofsub-beams, at a first collection of deflectors of a plurality ofdeflectors of a second element and simultaneously changing a spatialorientation of at least some deflectors of a second collection ofdeflectors of said plurality of deflectors in a deflection time periodthat is greater than said temporal pulse separation; and at said firstelement, redirecting, in said redirection time period said selectableangles of said plurality of sub-beams to at least some deflectors ofsaid second collection of deflectors.
 22. The method claimed in claim 21and wherein said providing comprises generating said pulsed beam ofradiation, said pulsed beam including a pulsed laser beam, using atleast one pulsed laser.
 23. The method claimed in claim 22 and whereinsaid at least one pulsed laser is a Q-switched laser.
 24. The methodclaimed in claim 21 and wherein said providing comprises generating saidbeam using a Q-switched laser.
 25. The method claimed in claim 21 andwherein said splitting also comprises: providing an acousto-opticaldeflector as said first element; and controlling said acousto-opticaldeflector.
 26. The method claimed in claim 25 and wherein saidcontrolling comprises: generating an acoustic wave; and determining saidselectable number of sub-beams.
 27. The method claimed in claim 25 andwherein said controlling comprises: generating an acoustic wave; anddetermining said selectable angles of said sub-beams.
 28. The methodclaimed in claim 26 and wherein said controlling also comprises:determining said selectable angles of said sub-beams.
 29. The methodclaimed in claim 28 and wherein generating said acoustic wave comprises:generating a plurality of spatially distinct acoustic wave segments; anddefining each spatially distinct acoustic wave segment by a portion of acontrol signal having a distinct frequency.
 30. The method claimed inclaim 29 and also comprising: determining a corresponding spatiallydistinct angle of a corresponding sub-beam from said each spatiallydistinct acoustic wave segment, said distinct angle being a function ofthe frequency of the portion of the control signal corresponding to saidacoustic wave segment.
 31. The method claimed in claim 29 and alsocomprising: determining the number of corresponding sub-beams from thenumber of said spatially distinct acoustic wave segments.
 32. The methodclaimed in claim 22 and also comprising: providing said plurality ofdeflectors of said second element, wherein each of said plurality ofdeflectors is mounted on at least one selectably tilting actuator. 33.The method claimed in claim 32 and wherein said at least one actuatorcomprises a piezoelectric device.
 34. The method claimed in claim 32 andwherein said at least one actuator comprises a MEMs device.
 35. Themethod claimed in claim 21, wherein: a number of deflectors in saidplurality of deflectors of said second element exceeds a maximum numberof said plurality of; and further comprising.
 36. The method claimed inclaim 21 and wherein said splitting comprises splitting said beam intosaid plurality of sub-beams all lying in a plane.
 37. The method claimedin claim 35 and wherein said second element comprises said plurality ofdeflectors, wherein said deflectors are selectable spatial orientationdeflectors and are disposed in a two dimensional array.
 38. The methodclaimed in claim 37 and also comprising: directing said plurality ofsub-beams to a third element comprising an array of fixed deflectors.39. The method claimed in claim 21 and also comprising: using saidplurality of sub-beams to remove a portions of said substrate atspecific locations.
 40. A method for delivering energy to a substrate,comprising: at a first element, receiving a pulsed beam of radiationincluding multiple pulses separated by a temporal pulse separation, andsplitting said pulsed beam into a plurality of sub-beams of radiation,wherein said plurality of sub-beams is a selectable number of sub-beamschangeable in an amount of time less than said temporal pulseseparation; during a first time interval, directing said plurality ofsub-beams onto at least some of a first collection of deflectors of aplurality of selectably positionable deflectors of a second element, andsimultaneously, changing an orientation of at least one of a secondcollection of deflectors of said plurality of selectably positionabledeflectors of said second element; and during a second time interval,directing said plurality of sub-beams onto at least some of said secondcollection of deflectors; wherein said first time interval and saidsecond time interval are each longer that said temporal pulseseparation.
 41. The method claimed in claim 40 and also comprising:generating said pulsed beam of radiation using at least one pulsedlaser.
 42. The method claimed in claim 41 and wherein said at least onepulsed laser is a Q-switched laser.
 43. The method claimed in claim 40and also comprising: generating said pulsed beam of radiation using aQ-switched laser.
 44. The method claimed in claim 40 and wherein saiddirecting during said first interval and said directing during saidsecond interval comprises: directing each of said plurality of sub-beamsin a selectable direction.
 45. The method claimed in claim 40, whereinsaid splitting said pulsed beam into a plurality of sub-beams alsocomprises: directing each of said plurality of sub-beams in a selectabledirection, wherein said selectable direction is changeable in an amountof time less than said temporal pulse separation.
 46. The method claimedin claim 45 wherein said splitting and said directing also comprises:providing an acousto-optical deflector as said first element; andcontrolling said acousto-optical deflector.
 47. The method claimed inclaim 46 and wherein said controlling comprises: generating an acousticwave; and determining said selectable number of sub-beams.
 48. Themethod claimed in claim 46 and wherein said controlling comprises:generating an acoustic wave; and determining said selectable directionsof said sub-beams.
 49. The method claimed in claim 47 and wherein saidcontrolling also comprises: determining said selectable directions ofsaid sub-beams.
 50. The method claimed in claim 49 and wherein saidgenerating an acoustic wave comprises: generating a plurality ofspatially distinct acoustic wave segments; and defining each spatiallydistinct acoustic wave segment by a portion of a control signal having adistinct frequency.
 51. The method claimed in claim 50 and alsocomprising: determining a corresponding spatially distinct direction ofa corresponding sub-beam from said each spatially distinct acoustic wavesegment, said distinct direction being a function of the frequency ofthe portion of the control signal corresponding to said acoustic wavesegment.
 52. The method claimed in claim 50 and also comprising:determining the number of corresponding sub-beams from the number ofsaid spatially distinct acoustic wave segments.
 53. The method claimedin claim 40 and wherein each of said selectably positionable deflectorscomprises a reflector mounted on at least one selectably tiltingactuator.
 54. The method claimed in claim 53 and wherein said at leastone actuator comprises a piezoelectric device.
 55. The method claimed inclaim 53 and wherein said at least one actuator comprises a MEMs device.56. The method claimed in claim 40 and wherein said first collection ofdeflectors includes a number of deflectors which a maximum number ofsaid plurality of sub-beams.
 57. The method claimed in claim 40 andwherein said selectable number of sub-beams all lie in a plane.
 58. Themethod claimed in claim 40 and wherein said plurality of selectablypositionable deflectors of said second element comprises a twodimensional array of selectably positionable deflectors.
 59. The methodclaimed in claim 58 and also comprising: deflecting said plurality ofbeams at a third element comprising an array of fixed deflectors. 60.The method claimed in claim 40 and also comprising: during said firstinterval, using said plurality of sub-beams to remove portions of saidsubstrate at a first plurality of locations, and during said secondinterval, using said plurality of sub-beams to remove portions of saidsubstrate at a second plurality of locations.